(a) Technical Field
The present disclosure relates to a system and a method for controlling an engine clutch of a hybrid vehicle. More particularly, the present disclosure relates to a system and a method for controlling an engine clutch of a hybrid vehicle, which constantly maintains the acceleration of the vehicle before and after release of an engine clutch to prevent a driver from feeling a sense of difference due to a change in inertia when the engine clutch is released.
(b) Background Art
Among green vehicles (e.g., environmentally friendly vehicles), a hybrid vehicle is a vehicle that uses an engine together with a motor as a power source, to promote the reduction in emission of exhaust gas and the improvement of fuel efficiency. A power transmission system for separately transmitting power of the engine or motor to drive wheels or simultaneously transmitting power of the engine and motor to the drive wheels is mounted within the hybrid vehicle.
A power transmission system for a hybrid vehicle, i.e., a powertrain, as shown in FIG. 1, includes an engine 10 and a motor 12, arranged in series, an engine clutch 13 disposed between the engine 10 and the motor 12 and configured to transmit or interrupt power of the engine, an automatic transmission 14 configured to vary a speed of power of the motor or the motor and engine and output the power to drive wheels, a hybrid starter generator (HSG) 16 connected to a crank pulley of the engine to perform engine starting and power generation, and the like. The power transmission system is divided into an engine clutch front part 100 and an engine clutch rear part 200 based on the engine clutch 13.
The power transmission system for the hybrid vehicle is of a type in which the motor is mounted to a side of the automatic transmission. The power transmission system is called as a Transmission Mounted Electric Device (TMED). The power transmission system provides driving modes including an electric vehicle (EV) mode that is a pure electric vehicle mode using power of the motor, a hybrid electric vehicle (HEV) mode in which the motor is used as an auxiliary power source while using the engine as a main power source, a regenerative braking (RB) mode in which braking energy or inertia energy of the vehicle produced by braking or during driving by inertia is recovered through power generation of the motor and is charged in a battery, and the like.
The HEV mode refers to a mode in which when driving such as starting, acceleration or hill climbing (e.g., driving on an incline) is required in which a substantial load is applied to the engine, a main relay is on simultaneously when the engine clutch is engaged, allowing the vehicle to be driven by a sum of output torques of the engine and the motor. In the EV mode in which the vehicle is driven using the motor, the main relay is on simultaneously when the engine clutch is disengaged, allowing the vehicle to be driven by the output torque of the motor.
When the driving mode is transferred from the EV mode to the HEV mode, the engine clutch is engaged. For example, after the speeds of both ends of the engine clutch, (i.e., the output speeds of the engine and the motor are synchronized together with cranking by an integrated starter generator (ISG)) the engine clutch is engaged, to perform the transfer of the driving mode to the HEV. In the HEV mode, as shown by a dotted line box in FIG. 1, the engine clutch front part 100 including the engine 10 and the engine clutch rear part 200 including the motor 12 operate as one rigid body. In the EV mode, the engine clutch front part 100 and the engine clutch rear part 200 operate as independent rigid bodies.
Therefore, in the transfer of the driving mode between the HEV mode and the EV mode, one rigid body is suddenly changed into two rigid bodies, or two rigid bodies are suddenly changed into one rigid body. Hence, a change occurs in inertia or the like, and vibration, shake or the like, caused by the change in inertia, is delivered to a driver causing the driver to feel a sense of difference, that is, to feel the vibration, jerk, shock, or the like. In other words, as the engine clutch front part and the engine clutch rear part, constituting one rigid body, operate as independent rigid bodies when the engine clutch is released, a change in inertia occurs. Therefore, the driver feels a sense of difference due to a change in acceleration of the engine clutch rear part, caused by the change in inertia.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.